1. Field of the Invention
The present invention relates in general to receiving, processing, and rendering two-dimensional and three-dimensional images, and more specifically a novel television set that operates in multiple image presentation modes able to render planar, stereoscopic, and/or autostereoscopic images.
2. Description of the Related Art
Current television sets serve a wide variety of purposes and display images with different formats. Many of today's television sets are able to display National Television System Committee (NTSC) images, high-definition television (HDTV) images, and digital images originating from a computer, digital camera, or other image capture devices. To properly display each of these image types, television sets may support a wide range of image resolutions and different aspect ratios. Often only a portion of the television display screen contains a viewable image since the very shape of the image changes depending on the content image resolution and aspect ratio. Thus, users of today's modern television sets have become accustomed to a variable viewing experience in which different types of content are presented on the display screen.
In addition, the user of a typical modern television set may obtain input images from more than one signal source. Television signals sources include signal transmission over-the-air, by physical cable such as broadband cable, by gaming consoles, and by prerecorded devices such as DVD players and cameras. Television sets supporting these signal sources provide a great deal of variety in the viewing experience, and indeed, this is part of the enjoyment of a modern television or video viewing experience.
Published concepts for stereoscopic television receivers support only one stereoscopic mode, either using an autostereoscopic display wherein wearing a form of selection device is not required for each observer, or using a plano-stereoscopic display (a two view stereoscopic image) in which all observers must wear a selection device, usually glasses, for proper image viewing.
Problems exist in single stereoscopic mode television designs that can result in a limited viewing experience, since stereoscopic content may be optimized for one kind of selection technique. Certain stereoscopic content conforms to a specification that generates images best viewed when a user wears selection device glasses, such as polarizing analyzing eyewear, and other content conforms to specifications that produce images best viewed autostereoscopically. For example, plano-stereoscopic images can have a larger parallax budget than autostereoscopic images. Autostereoscopic images often cannot make images appear to be very far off the screen without loosing sharpness whereas plano-stereoscopic images can. Therefore for content that depends on substantial off-screen effects, a plano-stereoscopic image may be superior. Moreover, some content may, for aesthetic reasons, be better viewed either with glasses or without glasses. For example, audience members/observers may watch a two-dimensional show on a single mode planar image television set supporting the NTSC standard. A content provider or advertiser typically creates three-dimensional stereoscopic content with the intent to engage and motivate the viewing audience into watching his commercial. Under typical circumstances, observers of a single mode planar image television do not require selection devices to properly view the show. When the commercial is presented, viewers will not benefit from the received three-dimensional stereoscopic content rendered, since the television set supports only a single mode, in this example a two-dimensional planar image. In this situation the advertiser's goal of engaging and retaining the viewing audience is not realized.
In another example, audience members may view a two-dimensional show on a single mode planar image television set supporting the HDTV protocol. A content provider or advertiser again creates three-dimensional autostereoscopic content with the intent to engage and motivate the viewing audience into watching his commercial. Observers of the single mode HDTV television do not require selection devices to properly view the two-dimensional show. When the commercial is presented, observers will not benefit from the received autostereoscopic content, since the television set supports only a single planar image mode, in this example a three-dimensional autostereoscopic image. Again, the advertiser's goal of engaging and retaining the viewing audience is not realized.
In both cases, the advertiser would be better served if the television set or display device could automatically present stereoscopic images to the viewer. In this case autostereoscopic images would be preferred because the viewer would not need to be actively reminded to don stereoscopic eyewear.
Required selection devices (such as selection device eyewear, e.g. glasses) for proper stereoscopic can be cumbersome from a viewer point of view. In the home environment, viewers wearing appropriate eyewear can impede or completely prevent people from performing normal daily tasks. Repeatedly having to put the glasses on and then having to take them off can create a vexing experience for many observers, especially when one considers how easily devices of this kind are lost. Consider television remote controls, whose disappearance is frequently the source of irritation in many households. While three-dimensional passive and active eyewear can provide an excellent stereoscopic viewing experience, their awkward use may not find acceptance with the viewing public. Currently, there is no unanimity amongst those in the television retail field with regard to the issue of whether or not viewers will accept wearing selection device eyewear.
Autostereoscopic images provide a novel viewing experience. However, autostereoscopic images can fail to reveal the depth and/or sharpness as when the same images are presented plano-stereoscopically and watched by observers wearing selection device eyewear. Autostereoscopic displays have traditionally been limited and do not provide the depth exhibited by plano-stereoscopic displays. Image selection for autostereoscopic displays occurs at the plane of the display screen, rather than at the eyes of the viewer as is the case for plano-stereoscopic displays. Moreover, one issue with autostereoscopic displays is the need for a multiplicity of images to be rendered to deliver images across a large viewing zone. A large viewing zone is beneficial because viewers cannot always be expected to carefully position themselves directly in front of the television set.
In addition, autostereoscopic presentation requires the display designer to carefully choose the disposition of pixels. The designer may choose to designate the pixels in a manner that allows increased resolution of individual image views, or to deploy the pixels in a different manner that affords an increase in the number of image views. Some compromise must be incorporated into the design of autostereoscopic television sets with regard to the number of perspective image views supported and to the optics that operate in conjunction with the display screen to provide an adequate angle of view. In such a design, designers must be aware that as the angle of view increases, the stereoscopic beneficial effect decreases. Thus autostereoscopic displays that provide a wide viewing angle are problematic in that the effective bandwidth requirements are much greater than for a plano-stereoscopic display.
Since plano-stereoscopic displays have certain strengths an weaknesses, i.e., great depth and sharpness but requiring the use of eyewear, and autostereoscopic displays similarly have certain strengths and weaknesses, i.e., no requirement for eyewear but comparatively limited sharpness and depth, it is advantageous to offer an architecture and design that can render multiple display modes for the accurate presentation of two-dimensional (planar) and three-dimensional images (plano-stereoscopic and autostereoscopic) that overcomes certain television set display issues present in previous designs.